The most popular form of toilet is a flush toilet. A flush toilet is a toilet that disposes of human waste by using water to flush it through a drainpipe to another location. A typical example of this is a close coupled cistern type of flush toilet illustrated in FIG. 1. A close coupled cistern type of toilet means that the water cistern is closely coupled to the toilet bowl. In FIG. 1, the toilet comprises a toilet bowl 90, a tank 94 and a tank cover 96. The typical tank volume is about 1.6 gallons, but the trend is towards smaller volumes.
The flushing mechanism in typical toilet systems provides a large flow of water into the bowl. The flushing mechanism usually incorporates one or more parts of the following designs: 1. a tank or cistern (i.e. the tank 74); 2. a tank fill valve (i.e. the fill valve 2 in FIG. 2); or 3. a bowl, a loo or a pan, which is the part of the toilet that receives bodily waste (i.e. the toilet bowl 90).
In a tank-based system, the storage tank (or cistern) collects between 6 and 17 liters of water over a period of time. This system is suitable for locations plumbed with ½″ (15 mm) or ⅜″ (10 mm) water pipes. The storage tank is kept full by a tank fill valve. The storage tank is usually mounted directly upon the bowl (close coupled cistern type), although some tanks are mounted on the wall a few feet above the bowl in an attempt to increase the flush water pressure as it enters the bowl.
FIG. 2 illustrates that in tanks using a flapper flush valve, the outlet at the bottom of the tank is covered by a buoyant plastic cover or flapper 6, which is held in place against a fitting (i.e. the flush valve seat 14) by water pressure. To flush the toilet, the user pushes a lever 8, which lifts the flush valve flapper 6 from the valve seat 14. The valve 6 then floats clear of the seat, allowing the tank to empty quickly into the bowl via a flush tube 12. As the water level in the tank drops, the flush valve flapper 6 falls back to the bottom, stopping the main flow to the flush tube 12.
Because the tank water level has yet to reach the fill line, water continues to flow from the tank 4 and bowl fill tubes 5. When the water again reaches the fill line 10, the float 1 will release the fill valve shaft 11 and water flow will stop. Other components of this system are a fill valve 2, a lift arm 3, an overflow tube 7, a chain 9 and a cistern 14. The float 1 can be a ball type float like in FIG. 2, or it can be another type of float, such as a concentric float 20 shown in FIG. 3.
In most locations, toilets use the potable water supply for supplying the water to the cistern. There is a need to conserve potable water or generally tap water. Toilet flushing does not need to be done with potable water (tap water) and hence there is a need for an alternative supply of water for flushing toilets. The most obvious alternative supply for flushing the toilets is to use captured or harvested rainwater. Rainwater can be captured or harvested from solid surfaces such as roofs and stored in a rainwater holding tank. This water is perfectly fine for flushing toilets. Connecting the rainwater supply to a single toilet is currently being done and is very straightforward. However, rainwater supply is not constant and is not always available. Hence, a reliable backup water supply and an improved system for using the backup water supply are needed for those instances when the rainwater tank is empty.